脱落酸和激动素对女贞叶气孔开闭的调节

叶气孔的开闭关系到植物同外界气体的交换,它对光合作用、呼吸作用和蒸腾作用均有很大影响。引起气孔运动的机理很复杂。前人的工作表明,激素亦参与气孔开闭的调节。如脱落酸(ABA)促进气孔的关闭,而激动素(KT)则促进气孔的开启。但这方面的研究多数是以草本植物进行的,木本植物的资料则少见。而这对控制干旱地区树木的     

有些植物的叶子为什么会开闭?

有些植物,如豆科植物等,它们的叶子会昼开夜闭,这是什么原因呢？日本一个科研小组对豆科植物叶子的昼开夜闭现象进行了潜心的研究,发现这种有规律的开闭运动,是由不同的两种化学物质互相作用而产生的。两年前,他们从豆科的臭草和决明属植物中分离出了使叶子闭合的催眠物质。它是一种结构比较简单的白屈菜酸的钾盐。最近,他们又从豆科植物中分离出一种使叶子展开的物质,这也是一种钾盐。通过实验证明,正常情况下,豆科植物中的这两 种化学物质保持平衡存在。专家们认为,豆科植物叶子的开闭运动,是由于叶子柄部的运动组…     

蚕豆气孔运动中水通道和离子通道的作用和地位的探讨

 用不同浓度HgCl2、LaCl3和TEACl (Tetraethylammonium chloride)处理蚕豆(Vicia faba)叶片下表皮条,发现HgCl2能显著抑制气孔开闭,Ca2+通道阻塞剂LaCl3或K+通道阻塞剂TEACl处理也都有一定程度的抑制。三者的作用效果HgCl2>>LaCl3>TEACl。用HgCl2+LaCl3、HgCl2+TEACl或HgCl2+LaCl3+TEACl处理,则气孔开闭运动几乎完全被抑制。表明：蚕豆气孔运动中,保卫细胞胀缩主要是水通道直接参与保卫细胞与叶肉细胞间水流的调节引起的,离子通道起间接次要作用,二者共同引起保卫细胞体积变化而导致气孔开闭。     

橡胶树叶片气孔开度与主要气象因子的关系

橡胶树叶片的气孔和其它植物的气孔一样,具有借着其开闭运动而调节植物体与大气之间气体交换的主要功能。因而,光合、呼吸及蒸腾等生理作用同气孔运动之间有着密切的关系。本文着重研究橡胶树叶片气孔运动规律与叶面光强、叶面温度和大田相对湿度等主要气象因子的关系。希望通过对主要气象因子的测定建立多元回归方程来预测气孔开度,以便     

向日葵叶片的有机酸

有机酸是植物代谢的重要产物之一.其作用有五点:①作为代谢的中间产物(如丙酮酸、α-酮戊二酸),可进一步转化为其他化合物;②构成植物体内的缓冲体系(如柠檬酸),使酸碱度变化不大,创造一个比较稳定的内环境,从而使各种生理生化过程有序地进行;③中和植物体内过多的阳离子,例如草酸可与钙离子结合,生成草酸钙结晶;④参与调节气孔的开闭运动,如苹果酸;⑤通过四碳二羧酸途径固定CO_2,使C_4植物的光合速率大大提高. 本文主要介绍向日葵在开花期、乳熟期、完熟期时叶片中有机酸含量的动态变化.     

矮嵩草草甸主要植物气孔分布及开闭规律与蒸腾强度的关系

本文研究了高寒矮嵩草草甸6种植物叶片气孔的分布、密度和开闭日变化规律与蒸腾强度的关系。结果表明：多数植物上下表皮均有气孔分布,而矮嵩草的气孔集中分布在下表皮,羊茅的气孔集中分布在上表皮。同一植物类群中,叶片气孔密度大者,植物蒸腾强度也相对较高。气孔日变化是在日出后,随气温和大气湿度的变化而变化,在9时和午后3时气孔几乎全部张开,然后逐渐关闭。植物蒸腾强度随气孔开闭而发生变化,矮嵩草的蒸腾强度在11时左右达到峰值;垂穗披碱草和美丽风毛菊是在午后1时达到峰值,植物没有“午睡” 现象。     

茉莉酸甲酯诱导保卫细胞气孔关闭的信号转导机制

气孔是由植物器官表面成对的保卫细胞围成的小孔,气孔运动控制气体交换,与植物逆境应答和生长发育等生物学过程密切相关,受多种因子调控,茉莉酸甲酯(MeJA)是其中之一。与ABA类似,MeJA也可诱导气孔关闭,但是其机理尚不清楚。该文综述了近年来MeJA调控气孔运动的信号转导机制进展,包括Ca2+、胞质pH、活性氧和NO等第二信使对气孔开闭的影响以及COI1、JAR1、RCN1和TGG1/2等信号组分之间的调控关系,并讨论了保卫细胞中MeJA与ABA信号途径的相互作用。     

长白山野生经济植物数据库建立与应用研究

通过资源调查,实地拍摄,全面收集长白山野生经济植物的相关资料,用现代信息发展的数据管理技术,研究设计软件,组织构建整个检索系统,为研究长白山植物提供了第一手材料,对合理开发利用长白山资源,保护生态环境和植物物种基因起到了重要作用。     

外源ABA、NO和H2O2对葱莲花瓣及叶片表皮气孔开闭的影响

以葱莲(Zephyranthes candida)为材料,研究不同浓度外源脱落酸、硝普钠(sodium nitroprusside,SNP)及过氧化氢对花瓣和叶片表皮气孔开闭的影响,以期为三者在切花保鲜中的应用提供新的依据。实验结果表明,10~1000 μmol/L脱落酸和硝普钠均能不同程度地引起花瓣和叶片表皮气孔关闭,且花瓣气孔较叶片气孔有更高的敏感性。过氧化氢对叶片表皮气孔开闭的影响大于对花瓣气孔的影响,花瓣表皮的气孔孔径仅在1000 μmol/L处理时变化显著。这说明在外源信号物质延缓切花衰老的过程中,花瓣表皮气孔的运动也可能起到了一定的作用。适当外源信号物质处理能诱导花瓣表皮气孔关闭,从而使花瓣的蒸腾作用减小,维持植物体内水势,延缓切花衰老。     

泥炭藓及其孢子萌发和有性生殖

将泥炭藓孢子萌发为配子体和有性生殖及精子形态等细节,用作者拍摄的活体照片,介绍给读者,以期对植物教学有所补充。     

The problem of shot selection in basketball

In basketball, every time the offense produces a shot opportunity the player with the ball must decide whether the shot is worth taking. In this article, I explore the question of when a team should shoot and when they should pass up the shot by considering a simple theoretical model of the shot selection process, in which the quality of shot opportunities generated by the offense is assumed to fall randomly within a uniform distribution. Within this model I derive an answer to the question “how likely must the shot be to go in before the player should take it?” and I show that this lower cutoff for shot quality depends crucially on the number of shot opportunities remaining (say, before the shot clock expires), with larger demanding that only higher-quality shots should be taken. The function is also derived in the presence of a finite turnover rate and used to predict the shooting rate of an optimal-shooting team as a function of time. The theoretical prediction for the optimal shooting rate is compared to data from the National Basketball Association (NBA). The comparison highlights some limitations of the theoretical model, while also suggesting that NBA teams may be overly reluctant to shoot the ball early in the shot clock.     

Can Ingestion of Lead Shot and Poisons Change Population Trends of Three European Birds: Grey Partridge,Common Buzzard,and Red Kite?

Little is known about the magnitude of the effects of lead shot ingestion alone or combined with poisons (e.g., in bait or seeds/granules containing pesticides) on population size, growth, and extinction of non-waterbird avian species that ingest these substances. We used population models to create example scenarios demonstrating how changes in these parameters might affect three susceptible species: grey partridge (Perdix perdix), common buzzard (Buteo buteo), and red kite (Milvus milvus). We added or subtracted estimates of mortality due to lead shot ingestion (4–16% of mortality, depending on species) and poisons (4–46% of mortality) reported in the UK or France to observed mortality of studied populations after models were calibrated to observed population trends. Observed trends were decreasing for partridge (in continental Europe), stable for buzzard (in Germany), and increasing for red kite (in Wales). Although lead shot ingestion and poison at modeled levels did not change the trend direction for the three species, they reduced population size and slowed population growth. Lead shot ingestion at modeled rates reduced population size of partridges by 10%, and when combined with bait and pesticide poisons, by 18%. For buzzards, decrease in mean population size by lead shot and poisons combined was much smaller (≤ 1%). The red kite population has been recovering; however, modeled lead shot ingestion reduced its annual growth rate from 6.5% to 4%, slowing recovery. If mortality from poisoned baits could be removed, the kite population could potentially increase at a rapid annual rate of 12%. The effects are somewhat higher if ingestion of these substances additionally causes sublethal reproductive impairment. These results have uncertainty but suggest that declining or recovering populations are most sensitive to lead shot or poison ingestion, and removal of poisoned baits can have a positive impact on recovering raptor populations that frequently feed on carrion.     

“Hand down,Man down.” Analysis of Defensive Adjustments in Response to the Hot Hand in Basketball Using Novel Defense Metrics

The hot-hand phenomenon, according to which a player’s performance is significantly elevated during certain phases relative to the expected performance based on the player’s base rate, has left many researchers and fans in basketball puzzled: The vast majority of players, coaches and fans believe in its existence but statistical evidence supporting this belief has been scarce. It has frequently been argued that the hot hand in basketball is unobservable because of strategic adjustments and defensive interference of the opposing team. We use a dataset with novel metrics, such as the number of defenders and the defensive intensity for each shot attempt, which enable us to directly measure defensive pressure. First, we examine how the shooting percentage of NBA players changes relative to the attributes of each metric. We find that it is of lesser importance by how many defenders a player is guarded but that defensive intensity, e.g., whether a defender raises his hand when his opponent shoots, has a larger impact on shot difficulty. Second, we explore how the underlying metrics and shooting accuracy change as a function of streak length. Our results indicate that defensive pressure and shot difficulty increase (decrease) during hot (cold) streaks, so that defenders seem to behave according to the hot-hand belief and try to force hot players into more difficult shots. However, we find that shooting percentages of presumably hot players do not increase and that shooting performance is not related to streakiness, so that the defenders’ hot-hand behavior cannot be considered ecologically rational. Therefore, we are unable to find evidence in favor of the hot-hand effect even when accounting for defensive pressure.     

Lead shot ingestion by mourning doves on a disked field

Previous field studies of hunter-harvested mourning doves (Zenaida macroura) have reported the percentage of birds with ingested lead shot as 0.2–6.5%. To reduce the uncertainty concerning the number of doves that ingest shot, we conducted an experiment to test the proportion of mourning doves that ingested lead shot on the bare soil of a disked field (typical of a managed dove field) to simulate more natural feeding conditions. In each of 3 treatment groups of 80 birds, we exposed 35 birds to low-density lead shot (1.5 million shot/ha), and35 birds to high-density lead shot (29.5 million shot/ha), and 10 birds served as controls (no shot). We dosed 5 positive control birds with 2 lead shot each in trials 2 and 3. We scattered lead shot and mixed seed on the loosely packed soil of treatment cages and after 4 days of exposure, 2.9% of doves voluntarily ingested ≥1 lead shot. The proportion of birds that ingested shot when exposed to the high-density shot treatment (4.9%) was not different (P = 0.098) from that of the low-density shot treatment (1.0%). Lead concentrations in liver, kidneys, and blood reached maxima of 94.402 ppm, 346.033 ppm, and 13.883 ppm wet mass, respectively. Differences in delta-aminolevulinic acid dehydratase (ALAD) activity, packed cell volume, and heterophil:lymphocyte ratio (H:L) were greater posttreatment in doves that had ingested shot than in those that did not. The risk posed to mourning doves from lead shot ingestion can be reduced by banning lead shot on management areas or dove fields or disking fields after hunting season to reduce shot availability. © 2011 The Wildlife Society.     

Health effects following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards

Permanent approval of shot composed of tungsten-iron and tungsten-polymer for waterfowl hunting by the U.S. Fish and Wildlife Service was pending the results of the present study that examined the health and reproductive effects of the two shot types on mallards (Anas platyrhynchos) over a 150-day period. We collected data pertaining to the effects of tungsten-iron and tungsten-polymer shot on mortality, body weight, organ weight, tissue pathology, and shot erosion. Thirty-two bird groups (sexes equal) of adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). An additional 12 mallards (sexes equal) were dosed orally with eight #4 lead shot (positive control) on day 0 of the study. All lead-dosed ducks died by day 25, whereas no ducks died in the other treatment groups. Significant liver hemosiderosis was present in all control and tungsten-iron-dosed males, in five of eight control and three of eight tungsten-iron-dosed females, and in one tungsten-polymer-dosed male examined. The rate of shot erosion was highest for tungsten-polymer shot (99%), followed by tungsten-iron (72%), and steel (55%) shot. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards did not have deleterious health effects during the 150-day trial based on mortality, body weights, organ weights, and histology of the liver and kidneys.     

Rice Mutant Resources for Gene Discovery

With the completion of genomic sequencing of rice, rice has been firmly established as a model organism for both basic and applied research. The next challenge is to uncover the functions of genes predicted by sequence analysis. Considering the amount of effort and the diversity of disciplines required for functional analyses, extensive international collaboration is needed for this next goal. The aims of this review are to summarize the current status of rice mutant resources, key tools for functional analysis of genes, and our perspectives on how to accelerate rice gene discovery through collaboration.     

Changes in age and sex ratios amongst samples of hunter-shot wings from common duck species in Denmark 1982–2010

There are almost no long-term demographic monitoring programmes of commoner waterbird species, yet such data are fundamental to our understanding of drivers of population change. In the present study, we present annual age and sex ratios in samples of shot duck wings forwarded on a voluntary basis by hunters throughout Denmark from 1982 to 2010 for eight common quarry species. Wigeon, Shoveler, Pintail and Goldeneye showed statistically significant declines in the proportions of young birds in the samples, but only Wigeon showed a statistically significant decline in the proportion of females in the adult sample over this period. Amongst Wigeon, the proportions of first winter birds and females were lower amongst the sample shot over decoys compared with those shot without decoys, suggesting these two shooting methods differentially select for young birds and females. However, the slopes of declines in these proportions shot with and without decoys over time did not differ. We found no correlations between North Atlantic Oscillation index values and the proportions of young for any of the species or between May and June temperatures on the breeding areas of Wigeon and the proportions of young in samples derived the following winter. With the exception of Wigeon, little is known about how well the shot duck wing samples reflect the true ratios in the populations, and unravelling the error and bias associated with these samples remains a high future research priority. If long-term declines in age and sex ratio in the wing surveys reflect true trends in the Wigeon population as a whole, we have strong grounds for concern for this population, and effort should be invested in increased demographic surveillance to better understand the causes of these changes. We need improved methods to derive unbiased measures of annual breeding of our common duck species if we are to be better able to understand the population dynamics of these stocks and be effective in their management. In the meantime, the Danish wing survey represents a unique time series of reproductive success for many common migratory duck species and must be maintained and further exploited.     

A comparison of two methods to establish the prevalence of lead shot ingestion in mallards (Anas platyrhynchos) from The Netherlands

Two collection methods for screening the mallard (Anas platyrhynchos) population in the Netherlands for the ingestion of spent lead shot were compared. One method consisted of examination of gizzards from mallards shot by hunters (n = 2,859) and the other method consisted of examination of gizzards from mallards caught in duck traps (n = 865). The 95% confidence interval of lead shot ingestion in the mallard population estimated by the first method was 1.7 to 2.9% and by the second method 1.1 to 3.1%. These values were not significantly different. From the numbers of lead pellets embedded in the gizzard wall in hunter-killed and trapped mallards it was estimated that at least 22 to 68% of the trapped ducks had been hit by lead shot previously, but survived. Furthermore, this study shows that it is reasonable to assume that a substantial part of the pellets which are identified (in this study and other studies) as ingested, may well have been shot into the gizzard lumen at some time before the birds were actually killed. To avoid lead poisoning in mallards and in raptors depredating waterfowl hit by lead shot, a change to steel shot is advocated.